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Setting up your bulkhead

This is the procedure I used:

1) Complete tear down; even the differentials
(not to be confused with the bulkheads)
2) Top off the differential with 30K
(or whichever weight you want to use. 30K is stock)
3) Clean excess grease off of ring and pinion
4) Clean up the interior of the bulkhead
5) Add 4 shims to proper side of differential between bearing and differential.
(not bearing and bulkhead)
(my reason for this location: this side of the bearing is greased, allowing the shims to slide on each other; hopefully not wearing down their thickness)
6) Install internal parts of bulkhead
(differential, pinion, ect)
7) Lightly lubricate the ring and pinion with a dry lube.
(this is to help resist the attraction of dirt)
8) Bolt up the lower skid plate
(it holds the bottom half of the bulkhead together)
8) Install long bolt holding two halves together
(snug it up, do not over-tighten)
10) Spin the drive shaft attached to the pinion. It should spin with slight resistance. If you have to work to spin it, there are too many shims. Remove one shim, repeat the process.
With that being said: mine spun nicely except for one spot where the teeth on the ring had a few nubs. In that location, it was more difficult to spin, but not hard to spin. If that makes sense. lol

This is how I set mine up. I have had 0 issues with gear mesh... no clicking, even when slamming it into reverse or forward while it is still rolling. No issues with binding either. When I set it up, my theory was that the new ring and pinion need to wear into each other while pushing the flex of the plastic bulkhead near its max.

I ended up with 3 shims in each bulkhead.
Associated 21141. They come with 4 shims per pack.

I have yet to tear it down to see how things are wearing into one another, but I imagine that the tooth surfaces of the gears are shiny. Just as they are in a properly meshed 1:1.

Oh, a few more tips:
1) Pay attention to what side the ring is on in the bulkhead!
2) After setup, I did not go out and run a full pack through it. I ran it a little, then let it cool down. This might not matter at all, it is just how 1:1 gears are broke in.
3) Take your time. Don't be rushed. Setting this up properly will save you in the long run!

Make a note, 4 shims is not always needed, in my case I needed none on my new style bulkheads, on my wife's with old style bulkheads I needed only one, two was too much and caused binding. Four sounds like it would be overkill in most cases.

do you find you strip many of the screw holes on the bulkhead often? ive stripped the skidplate screw holes, the shock tower screw holes and the rear toelink holes many times. before you say that im not screwing properly, i have no other stripped holes on the car at all. all of the holes above should tighten to a stop, correct?

do you find you strip many of the screw holes on the bulkhead often? ive stripped the skidplate screw holes, the shock tower screw holes and the rear toelink holes many times. before you say that im not screwing properly, i have no other stripped holes on the car at all. all of the holes above should tighten to a stop, correct?

I bought a torque adjustable driver and once set to a light setting all screws/bolts on my merv are all exactly the same with no fear of stripping as the handle just spins when its tight enough

I think only one person ended up with four shims... in an aluminum bulkhead.
It is easier for most to "feel" proper shimming when they start with binding gears rather than loose gears; and you got to start somewhere. lol

I think only one person ended up with four shims... in an aluminum bulkhead.
It is easier for most to "feel" proper shimming when they start with binding gears rather than loose gears; and you got to start somewhere. lol

We must've got a set made on Monday, my kids Summit took four also.....

whats the thickness of the shims in the associated set? i only have metric shims, in mm 0.1, 0.2 and 0.3
i screwed up two diffs today with 1 shim in both front and back bulkhead.
should i add in a bunch of shims and take them off until theres no binding?

whats the thickness of the shims in the associated set? i only have metric shims, in mm 0.1, 0.2 and 0.3
i screwed up two diffs today with 1 shim in both front and back bulkhead.
should i add in a bunch of shims and take them off until theres no binding?

Keep adding them until there is very little side to side movement. My Integy rear bulkhead required 4 shims in order to be tight.

The stock bulkheads are made to have the proper clearance and mesh for the gears... until the plastic they are made of flexes, causing mesh issues. Shims push the flex to the max, forcing the mesh to be tighter and hold under greater stress. I do not see the need to add any shims to the opposite side of the ring gear unless, perhaps, you are using an poorly machined or miss-machined aluminum bulkhead. If the mesh is too tight, remove a shim as stated in the instructions. Chances are the bulkhead flex has reached its' max and is the cause of the binding issues.

Upon further thought...
I suppose a few stock bulkheads could develop a greater amount of flex and require a need for opposing side shims... but I believe that this would be an exception to the "norm" and adding this to the general shimming procedure will just murk up the water; so to speak.

-- I do not know why this has not been stickied. That decision is completely up to the moderators... I think.
But, if this topic is really that crucial, constant conversation on it will keep it to the top anyway. lol

-- I do not know why this has not been stickied. That decision is completely up to the moderators... I think.
But, if this topic is really that crucial, constant conversation on it will keep it to the top anyway. lol

^You're just about correct. The moderators have the power to sticky threads (I would know from my FAQ, of course), and if it's not worthy of a sticky and has wrong information (like the FAQ...lol) it won't be stickied. I honestly do think that this is worthy of a sticky but many moderators do not like sticky threads because they simply crowd up the forum.

Is it possible to determine if shims are needed by pushing the diff. assembly back and forth within the bulkheads once the drive shafts are off? That's how I've done it on various transmission gears in other vehicles, but I'm new to the merv.

Is it possible to determine if shims are needed by pushing the diff. assembly back and forth within the bulkheads once the drive shafts are off? That's how I've done it on various transmission gears in other vehicles, but I'm new to the merv.

thats how i did it. but because the bulkhead flexes it is best to shim it but keep feeling for any binding

Make a note, 4 shims is not always needed, in my case I needed none on my new style bulkheads, on my wife's with old style bulkheads I needed only one, two was too much and caused binding. Four sounds like it would be overkill in most cases.

Great write up. I'm gonna try this tomorrow if our lhs has the shims. I'm getting a clicking and don't know if I tightened the dif screws to tight, if it's the ring/pinion or the clutch ( pinion/spur ). First mistake I did when trying to lubricate the dif ( to the driveshaft , not inside the dif ) was to use dif lube. Talk about a dumb move and a dirt magnet :/

aluminium bulkheads are great, i run the gpm unit with 2 shims on both front and rear. at first, i had binding issues with 2 shims on the front bulkhead, so i put only 1, this lead to the ring gear being chewed up on a 4s high speed run. if your going the gpm route, they ALL use 2 shims. very nicely cnc machined units, just pricey, but i guess all good things come at a price huh

2 shims was binding. One shim it didn't bind but I heard clicking. No shim was a lil sloppy but not bad at all. I ended up just cleaning the diffs adding new dif lube and going with one shim front and rear. Amazing what one tiny little washer can do lol